On Taiwan, Brzezinski said that since 1972, the US has formally accepted Beijing’s “one China” formula, while maintaining that neither side shall alter the “status quo” by force.

He added that Beijing reserves the right to use force, which allows Washington to justify its continued arms sales to Taiwan even though, in recent years, Taiwan and China have improved their relationship.

Brzezinski, national security adviser under former US president Jimmy Carter, wrote: “America’s decline, however, would increase Taiwan’s vulnerability, leaving decision-makers in Taipei more susceptible to direct Chinese pressure and the sheer attraction of an economically successful China.”

“That, at the least, could speed up the timetable for cross-strait reunification, but on unequal terms favoring the mainland [China],” he wrote.

At stake, he wrote, is a “serious collision with China.”

A number of US experts on China and Taiwan strongly disagreed with the analysis.

One of the experts said that Brzezinski had contributed to Taiwan’s political endangerment when he was in power.

Others said that China could be overtaken itself by an internal political crisis before unification with Taiwan might occur.

Yet another expert said there was a major difference between China’s “one China” formula and the US’ “one China” policy.

“The US has not ‘accepted’ China’s claim to Taiwan, but only ‘acknowledged’ it,” he said.

On South Korea, Brzezinski said that the US’ “decline” would confront Seoul with “painful choices” to either accept Chinese regional dominance and further reliance on China to rein in the nuclear-armed North or seek a much stronger “though historically unpopular” relationship with Japan.

At stake, he said, was military and economic security on the Korean Peninsula and a general crisis of confidence in Japan and South Korea regarding the reliability of the US’ existing commitments.